This invention relates to control assemblies and more particularly to control assemblies for transmissions.
Transmissions are well known in which ratio and direction changes are made by selective energisation of hydraulic clutches which are controlled by one or more hydraulic valves. It is also well known to provide a single control lever which operates on the valve(s) so that movement in a first plane selects forward or reverse direction and in a second plane selects ratio. A neutral condition is provided between forward and reverse. However, with such arrangements it is possible to move immediately from maximum forward speed to maximum reverse speed so that high loads are placed on the transmission. To prevent this, controls have been provided with a gate in the form of a U shaped slot so that movement from forward to reverse requires a ratio change to reduce vehicle speed. However, this arrangement is unsatisfactory from a safety point of view since a neutral ratio is only available by a compound movement in two planes and such movement may easily re-engage a ratio rather than neutral.
To overcome this an additional position has been made available in the second plane which gives a neutral condition. This not only requires more expensive control valves but means that for each direction change, a ratio and a direction clutch has to be engaged which results in an increased cycle time.
It is an object of the present invention to provide an improved form of control assembly which obviates or mitigates the above disadvantages.